O R I O N

[orangefj45]

Not sure if this is really much better than any of the other lock solutions shown so far, but it worked great last year on the trip down to the Rubithon from Portland, and back. No issues at all. I was going to fashion some sort of metal bar, but this HDPE prototype is so quiet and works great, I just left it in. It could for sure be made prettier, but doesn't bother me. I like that the shifter is able to move around and never really ride on the stop at all in normal driving. It only bumps into the plastic stop when it's working its way out of gear, but hasn't popped out once. I had all the parts in my garage already: a cheap cabinet hinge, some IKEA cutting board, a mismatched colection of hardware, and even the hose barb plug. It took a little bit of trial and error to make it the right size and placement so both the H and L settings still have some movement, but don't let it slip out of gear, but it has so far been 100%. Would take some adjustments to the design to use with a pretty boot, but I'm not too worried about pretty. The slotted foam keeps about as much noise out as the original rubber part, and I've driven it in Oregon rain a bunch and never had any water ingress. I'm calling this solved on my end. Any wear on the fork from the few seconds it's rubbing while trying to walk out of gear when rubbed up against the plastic lockout will likely take more time than I have left driving this to cause any problems.


View attachment 4112967

Great solution!!!

Georg @ Valley Hybrids

 

[Skillet]

My stolen fix works great. Too bad AA can’t make it right.

 

[fj40scottb]

Hi Everyone, been a very long time since I've popped over here at MUD. Glad to see all is well.

It's been a few years since I've thrown some love at the 40, so I have an Orion and twin sticks on order to replace my old 3-speed case behind my SM465. So I popped into this thread to see what's been the word on the street with Orion's. I was aware of the popping out of gear issue (used to have a 60 with an Orion, never popped out of gear but the detents were so dang stiff it was almost impossible to shift from 4-Lo to 4-Hi without getting out and going to the passenger side and pushing the shifter from a different angle). Sounds like the issues are still there and people are still chasing it to some degree.

I started reading back through the threads and it dawned on me in the age of AI, that why not let AI summarize things for me to catch me back up on the details. So I pointed ChatGPT at the forum and this thread and let it summarize this details on this issue.

Thought I'd share the summary to:
1) share with others, perhaps the summary will be helpful
2) see if AI actually got it right

Well if this helps anyone here it is, enjoy, or not.

ChatGPT's response:
Thought for 35s
I reviewed the relevant “popping out of gear” discussion across the IH8MUD Orion thread, including the early case-history posts and the later 2021–2025 follow-up posts. My takeaway: there is not one universally agreed single root cause, but the repeated pattern is very consistent.

Bottom line​

The Orion tends to pop out of gear when the Hi/Lo shift collar is being forced or vibrated toward neutral under coast/deceleration load, and the internal retention system — detent ball/spring/shift rail plus the engagement geometry of the gear teeth and collar — is not strong enough to keep it fully engaged.

The most common condition is deceleration or engine braking downhill, especially:

• High range while coasting downhill, including highway/downhill gravel-road situations.
• Low range on steep downhill descents, where engine braking loads the drivetrain hard.
• 3rd gear deceleration is mentioned more than once, likely because it creates a strong driveline back-load without the vehicle being at crawl speed.
• Some users report it getting worse once hot, after wear develops, or after miles accumulate.

Early examples set the pattern: one user reported case #100 popping out of high range while coasting downhill in 3rd gear; another reported low-range pop-outs on extreme downhills; another reported high-range pop-out “occasionally on road while decelerating.”

Probable root-cause stack​

1. Gear/collar engagement geometry appears to be the core issue​

Several posts point to the way the Orion gear dog teeth and the Hi/Lo sleeve engage. In later troubleshooting, NikP compared stock Toyota gear teeth to Orion gear teeth and observed that the Orion dog teeth appeared narrower and more pointed, which could allow more sleeve movement and provide a ramp-like path for the sleeve to disengage. He also quoted AA as acknowledging that angled teeth can cause the shift collar to release prematurely.

This lines up with the older related discussion where members argued that the dog-tooth profile/bevel/taper was a fundamental contributor, and that normal wear factors make it worse.

2. Excessive gear free-play/end-play or output-shaft/bushing clearance aggravates it​

One of the older technical posts says limiting free-play on the main shaft “lessens or completely removes” the popping issue. In that same discussion, a case that popped out of high range only when coasting downhill had about .025" free play, and the owner limited both gears to about .008" using stepped thrust washers; hard deceleration testing afterward stayed in gear.

Later posts repeat the same theme: output-shaft/bushing clearance, dog teeth, and the shift collar all matter. Peesalot specifically says that if the shaft-to-bushing clearance is loose, dog teeth are worn, or the detent system is not updated, the collar can be rattled or driven out of engagement.

3. Detent design matters, but detents alone do not always solve it​

The thread repeatedly references updated shift rails, deeper detents, detent ball/spring upgrades, and square-shouldered versus chamfered detents. One member reported that his issue was solved when chamfered shift detents were replaced with older-style square-shouldered detents; his theory was that chamfered shoulders let the detent ball ride out under load.

But the later posts make it clear that detents are not always enough. NikP had new gears, new output shaft, new Hi/Lo sleeve, and kit-supplied detent parts, yet still popped out of both 4Hi and 4Lo on downhill deceleration.

4. Driveline vibration can trigger or worsen it​

A recurring theory is that driveline vibration during deceleration helps shake the collar out of engagement. Peesalot specifically connects worn rear driveshaft slip-spline vibration on decel to rattling the collar, and later says that a balanced rear driveshaft with proper angles seemed to keep his case from popping out of high on decel.

This is especially relevant to SOA/lifted 40s with short rear driveshafts, steep driveline angles, or vibration under coast load.

5. Shifter/linkage can contribute, but should not be the thing retaining the case in gear​

Several posts distinguish between moving the range selector and retaining it. The shifter should be pressure-neutral and not rubbing the body or trans cover. If the linkage is loaded, heavy, loose, or interfering, it can help the problem happen. But the internal detents and gear/collar engagement should be what retains the gear.

Under what conditions does it happen?​

The strongest repeated pattern is:

Downhill deceleration / coast load / engine braking → drivetrain back-loads the transfer case → collar starts walking toward neutral → detent cannot hold it → shifter moves and case pops to neutral.

Specific examples:

• High range, coasting downhill in 3rd gear.
• Low range, extreme downhill descents.
• High range on-road while decelerating.
• High range on easy downhill gravel roads.
• 4Hi and 4Lo when decelerating or riding against engine back-pressure on a downslope.
• Compression braking/coasting downhill in gear, where the shifter can visibly drift toward neutral.

What fixes were reported?​

The fixes are mixed; some work for some cases, not all:

• Stepped thrust washers to limit gear free-play.
• Back-cut high-speed gear so the range shift collar does not interfere with the high-speed gear.
• New output shaft and high-speed gear, which solved one long-running case where AA suspected wear/wobble on a reused stock output shaft.
• Updated shift rail, detent ball, and spring, though not always sufficient.
• Square-shouldered detents instead of chamfered detents, which solved at least one case.
• Making sure linkage/shifter is fully engaging and not rubbing the body/trans cover.
• Balanced rear driveshaft and correct driveline angles, especially for high-range decel pop-out.
• External shifter locks/straps/bungees, which several owners use, but at least one experienced builder warned that forcing it to stay in gear does not remove the internal load and can wear the shift fork/collar over time.

My interpretation​

For your purposes, I would describe the root cause this way:

The Orion pop-out issue is caused by the range shift collar being driven out of full engagement under deceleration/engine-braking loads. The underlying contributors appear to be a combination of dog-tooth/shift-collar engagement geometry, gear free-play or shaft/bushing clearance, detent design/strength, wear in reused Toyota components, and driveline vibration. It most commonly happens on downhill coast or engine-braking conditions, in high range on road/downhill gravel and in low range on steep descents.

The important nuance: the detent is not the root cause by itself. It is the last line of defense. If the gear/collar geometry, clearances, or driveline vibration are pushing the collar toward neutral, the detent may simply be overwhelmed.